The ore content of ore mined from an ore mine is usually defined by taking samples of the ore in the mine and by analyzing them in a laboratory. The analyzing of the samples usually takes a couple of days. Based on the received results, the mined ore is generally separated to waste rock and ore to be taken to further processing.
After that the ore to be taken to further processing will be crushed into grains of a desired size, that in some cases are further agglomerated to pellets of a desired size, for example in an agglomeration drum, whereby for example sulfuric acid is added to the ore in connection with the pellet production in order to intensify the further processing. After that, the agglomerated ore is taken to the further processing or storage.
One method for further processing of ore, known in the art, is heap leaching, whereby the crushed and agglomerated ore is stacked into a heap of a desired art and form, liquid dissolvent being sprayed evenly onto said heap, consisting for example of acid and microbes in a biological dissolution procedure. In the biological dissolution procedure, at first sulfur acid is sprayed onto the heap, corroding the ore pellets in a suitable way, after which the microbes to be sprayed onto the heap access the metals to be corroded out of the ore. These microbes dissolve the metal contained in the ore, said metal flowing along with the microbes in the solvent on the bottom of the heap. From the bottom of the heap the concentrated solvent is collected for further treatment of the metal. In general, the metal is removed from the concentrated solvent in a desired way, whereby the reclaimed solvent with its microbes can be reused as a solvent in the heap leaching process.
In the heap leaching process also air can be blown to the heap, if necessary, to intensify the action of the microbes and to accelerate the leaching process. In addition, also nutrients can be brought for the microbes. If necessary, the heap can also be covered for example for maintaining a suitable temperature in the heap for the leaching process.
Alternatively, the heap leaching process can also be implemented by using only acid as a solvent.
The ore content of the ore mined from an ore mine, however, varies very much, because the ore content of the mined ore is determined from a large amount of ore only with a couple of laboratory samples. Due to this big variation of ore content, it is difficult to manage the efficiency of the further processing of the ore, because in general the norms for the further processing are defined specifically according to the average ore content. For example in the above mentioned heap leaching process, this means that the same quantity of solvent is sprayed for each portion of the heap. Therefore in many portions of the heap, too much liquid dissolvent will be sprayed, whereas in some portions there is not enough liquid dissolvent with respect to the ore content.